I've been making a few parts experimenting with cores as I go.  I'm favouring 200g/3mm pvc foam/200g OR 200g /3mm soric/200g.  I'm finding they feel equally stiff and weigh pretty much the same.  Obviously the soric cell is fairly soft but the structure makes it rigid.  The foam is harder but doesn't have the structure.  Has anyone performed break tests or have any other info that might discriminate between these two?